Ink-jet printers, in which an array of small ejectors are operated by digital data in real time to eject droplets of ink onto a sheet to create an image, are well-known. For high-quality ink-jet printing, certain improvements in the ultimate appearance of a print can be made by detailed manipulation of the timing of the activation of individual ejectors. For example, for a printhead having an array of ejectors arranged in an order 1, 2, 3, 4, 5, 6, 7, 8, activating the ejectors in order may result in droplets emitted from neighboring ejectors splashing against each other, thus resulting in undesirable print defects, such as satellite droplets. Within the short time frame in which a set of ejectors accesses a particular small area on a print sheet it may be more desirable to alter the ejection order along the array, such as an order over time of 1, 5, 2, 6, 3, 7, 4, 8: this order will ensure that an ejector to be activated is a number of ejectors away from the previous ejector that was activated, thus avoiding the splashing problem. Alteration of the specific activation order of ejectors in an array, of which the above is only one example, can be used to increase either throughput speed and/or print quality.
Another possible ink-jet printing method is to make available a "draft mode," in which only a subset of ejectors which would ordinarily be activated to print an image are in fact used. While such a draft mode will of course result in lower print quality, it may have the advantage of consuming less ink. One typical draft mode is "checkerboarding" the ink droplets in what is originally intended to be a full-black area. With checkerboarding, with every pass of ejector activations through the linear array, in one pass only even-numbered ejectors are enabled, while in a subsequent pass, only odd-numbered ejectors are enabled. This alternation of odd and even-numbered ejectors as the printhead moves across the sheet creates this checkerboarding effect.
It is a purpose of the present invention to provide an ink-jet printhead having circuitry thereon, which enables the selection of these and other various print modes. According to the present invention, various modes can be selected by sending certain mode signals to the printhead circuitry along with image data signals.